JP2017037103A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of controlling a position of a focus lens unit stably even when an error occurs in a signal for focus detection.SOLUTION: The imaging apparatus includes: a focus detection section for detecting a focus state of an imaging optical system; a zoom position detection section for detecting a zoom position of the imaging optical system; a focus position detection section for detecting a position of the focus lens unit of the imaging optical system; an adjustment section for adjusting the position of the focus lens unit of the imaging optical system; a storage section for storing a trajectory of the focus lens unit that is moved according to the change in the zoom position, so as to continue focusing on a subject at a constant distance; a determination section for determining reliability of output of the focus detection section; and a control section for switching operations between a first operation and a second operation, on the basis of the determination of the determination section. The first and second operations are to control the position of the focus lens unit according to the change in the zoom position. The control in the first operation is performed on the basis of the output of the focus detection section, while the control in the second operation is performed on the basis of information of the trajectories of the focus lens unit, stored in the storage section.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an imaging apparatus that performs position control of a focus lens based on a signal from an imaging element.

  2. Description of the Related Art In recent years, image sensors have advanced functions, and a system capable of detecting a so-called phase difference AF signal with the image sensor has been proposed. Conventionally, proposals have been made to use information on the imaging surface for focus detection, and Patent Document 1 proposes to adjust the optical system (focus adjustment) by feeding back the focus state.

  On the other hand, proposals have been made to adjust the optical system according to changes in the zoom state of the optical system. Japanese Patent Application Laid-Open No. 2004-228688 proposes maintaining a focus state by driving a focus lens in accordance with a change in a zoom state of an optical system.

Japanese Patent Laid-Open No. 55-40447 JP 52-114321 A

  However, Patent Document 1 does not describe processing when an error such as a decrease in the degree of coincidence of two images for phase difference detection or a sudden saturation of luminance occurs when used in the field. Therefore, there is a problem that the system tends to become unstable.

  Further, in Patent Document 2, since the focus lens is driven in accordance with the change in the zoom state without detecting the focus state of the image, there is a problem that errors are likely to accumulate in the lens positioning.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an imaging apparatus capable of stably performing focus lens position control even when an error occurs in a signal for focus detection. Is to provide.

  An imaging apparatus according to the present invention detects a focus detection unit that detects a focus state of a photographing optical system, a zoom position detection unit that detects a zoom position of the photographing optical system, and a position of a focus lens of the photographing optical system. A focus position detecting means, an adjusting means for adjusting the position of the focus lens of the photographing optical system, and a locus of the focus lens for continuously focusing on a subject at the same distance according to a change in the zoom position. Based on the output of the focus detection means, the storage means for storing, the determination means for determining the reliability of the output of the focus detection means, and the position of the focus lens according to the change of the zoom position are controlled. 1 according to the change in the zoom position based on the movement of the focus lens and information on the locus of the focus lens stored in the storage means. A second operation for controlling the position of Surenzu, characterized in that it comprises a control means for switching in response to determination of said determination means.

  According to the present invention, it is possible to provide an imaging apparatus that can stably control the position of the focus lens even when an error occurs in a signal for focus detection.

1 is a diagram showing a configuration of a camera system that is an embodiment of an imaging apparatus of the present invention. 1 is a block diagram showing a main part of an imaging apparatus according to an embodiment. The figure explaining basic zoom tracking operation. The figure explaining zoom tracking operation when an error occurs. The figure explaining another zoom tracking operation | movement. The figure explaining a focus detection part. The figure explaining the scene where the error of a focus detection tends to occur.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a configuration of a camera system that is an embodiment of an imaging apparatus according to the present invention. FIG. 1A is a central sectional view, and FIG. 1B is a block diagram illustrating an electrical configuration. .

  In FIG. 1A, a camera system 100 includes a camera body 1 and a lens unit 2 that is detachably attached to the camera body 1. The camera body 1 includes an electrical contact 11 with the imaging device 6, mechanical shutter 14, back display unit 9 a, electronic viewfinder 9 b, and lens unit 2. The lens unit 2 includes a photographing optical system 3 composed of a plurality of lenses along the optical axis 4. The lens unit 2 includes a lens position sensor 15 that detects the position of each lens group and outputs a position detection signal of each lens group.

  In FIG. 1B, the camera body 1 includes, as electrical blocks, a camera system control circuit 5, an image processing unit 7, a memory unit 8, an operation detection unit 10, a display unit 9 (a rear display unit 9a, an electronic viewfinder 9b. Including). The lens unit 2 includes a lens system control circuit 12 and a lens driving unit 13 as electrical blocks.

  The camera system 100 including the camera body 1 and the lens unit 2 is roughly composed of an imaging unit, an image processing unit, a recording / reproducing unit, and a control unit. The imaging unit includes a photographing optical system 3 and an imaging element 6, and the image processing unit includes an image processing unit 7. The recording / reproducing unit includes a memory unit 8 and a display unit 9, and the control unit includes a camera system control circuit 5, an operation detection unit 10, a lens system control circuit 12, a lens driving unit 13, and a lens position sensor 15. . The camera system control circuit 5 controls the overall system based on signals obtained from the camera body 1 and the lens unit 2. The lens driving unit 13 drives the focus lens 31, the shake correction lens, the diaphragm, and the like. The lens position sensor 15 detects the position of each lens group such as a zoom lens group and a focus lens group that constitute the photographing optical system 3 (zoom position detection, focus position detection). Further, the lens position sensor 15 has an accuracy suitable for performing zoom tracking described later.

  The imaging unit forms an image of light from the object on the imaging surface of the imaging element 6 via the imaging optical system 3. Since the focus evaluation amount and the appropriate exposure amount can be obtained from the signal of the image sensor 6, the imaging optical system 3 is adjusted based on these signals, thereby exposing the image sensor 6 with an appropriate amount of object light. A subject image can be formed in the vicinity of the image sensor 6.

  The image processing unit 7 includes an A / D converter, a white balance adjustment circuit, a gamma correction circuit, an interpolation calculation circuit, and the like, and generates a recording image. The color interpolation processing unit is provided in the image processing unit 7 and performs color interpolation (demosaicing) processing on the Bayer array signal to generate a color image. The image processing unit 7 compresses images, moving images, sounds, and the like using a predetermined method. Furthermore, the image processing unit 7 generates a shake detection signal based on a comparison between a plurality of images obtained from the image sensor 6. This operation will be described later. The memory unit 8 stores image data and the like. The camera system control circuit 5 outputs image data to the memory unit 8 and sends it to the display unit 9 to display an image to be presented to the user.

  The camera system control circuit 5 generates and outputs a timing signal at the time of imaging. In response to an external operation, the imaging unit, the image processing unit, and the recording / reproducing unit are controlled. For example, the operation detection unit 10 detects that a shutter release button (not shown) is pressed, and controls driving of the image sensor 6, operation of the image processing unit 7, compression processing, and the like. Further, the display of the image by the display unit 9 is controlled. Further, the rear display unit 9 a is a touch panel and is connected to the operation detection unit 10. The camera body 1 includes a mechanical shutter 14 and can perform exposure control of the image sensor 6 in response to a command from the camera system control circuit 5.

  Next, the adjustment operation of the photographic optical system 3 will be described. An image processing unit 7 is connected to the camera system control circuit 5, and a focal position and a diaphragm position are obtained based on a signal from the image sensor 6. The camera system control circuit 5 issues a command to the lens system control circuit 12 via the electrical contact 11, and the lens system control circuit 12 controls the lens driving unit 13. Furthermore, in the mode for performing camera shake correction, the shake correction lens is controlled via the lens driving unit 13 based on a signal obtained from an image sensor described later.

  The memory unit 8 records a locus of the focus lens (details will be described later) with respect to the zoom change. Further, the camera system control circuit 5 calculates the distance of the subject from the information in the memory unit 8 and the information in the lens position sensor 15, and calculates an appropriate focus lens position when a zoom change occurs. This is called an electronic cam.

  As will be described later, the image sensor 6 outputs a plurality of images from different viewpoints necessary for the phase difference AF, and the image processing unit 7 performs a so-called correlation calculation. That is, focus detection is performed by the image sensor 6 and the image processing unit 7. The position control of the focus lens is performed by the camera system control circuit 5, the lens system control circuit 12, and the lens driving unit 13.

  FIG. 2 is a diagram for explaining a main part of the camera system of the present embodiment. In FIG. 2, the focus detection unit 21 is provided in the image processing unit 7, and the electronic cam calculation unit 22 and the changeover switch 23 are provided in the camera system control circuit 5. The reliability determination unit 24 controls the operation of the changeover switch 23. The focus detection unit 21 detects information related to the focus (whether or not the area in which the main subject is present is in focus, and the direction and amount when the area is not in focus).

  Based on the signal output from the image sensor 6, the focus detection unit 21 in the image processing unit 7 obtains information regarding the focus. When the reliability determination unit 24 determines that the information detected by the focus detection unit 21 is appropriate, the changeover switch is in the state illustrated in FIG. 3, and the focus lens 31 is based on the signal from the focus detection unit 21. Position control is performed. Specifically, feedback control is performed on the focus lens 31 so as to maintain a state where the main subject is in focus. The lens system control circuit 12 outputs a command for performing this feedback control to the lens driving unit 13.

  On the other hand, when the reliability determination unit 24 determines that the signal obtained by the focus detection unit 21 is not appropriate, the changeover switch 23 is switched to be connected to the electronic cam calculation unit 22. Then, the position control of the focus lens 31 is performed based on the signal from the electronic cam calculation unit 22. Specifically, a command is issued from the lens system control circuit 12 to the lens driving unit 13 so as to maintain the previous focus state regardless of the state of the subject. When there is no change in the zoom state, the focus lens remains stopped, and when there is a change in the zoom state, a control called zoom tracking is performed. The zoom tracking operation will be described later.

  The electronic cam calculation unit 22 acquires the positions of the focus lens and the zoom lens from the lens position sensor 15 and obtains information regarding the focus state and the zoom state. Further, the subject distance corresponding to the case where the position of the focus lens and the position of the zoom lens are at the positions indicated by the lens position sensor 15 is calculated with reference to the memory unit 8. As will be described later, when the zoom state changes, it is necessary to appropriately drive the focus lens in order to maintain the focus state on the subject at the same distance. This operation is called a zoom tracking operation.

  Next, a method for determining whether the signal obtained by the reliability determination unit 24 in the focus detection unit 21 is appropriate or not will be described. As will be described later, when a signal necessary for the phase difference AF is obtained from the image sensor 6, the degree of coincidence of the two images in the correlation calculation can be used for the determination of reliability. As another method, in the case of using contrast AF, a signal in which the amount of change in contrast is made dimensionless with luminance can be used. As another method, the position of the subject on the object side can be observed in time series and its continuity can be used. In each of the determination methods described above, when the degree of coincidence between the two images is low, the change in the contrast signal is small, and the moving speed of the subject is too fast (when the focus position moves back and forth due to perspective conflict), It is determined that it is inappropriate to use the signal detected by the detection unit 21. And it switches to the control based on the signal of the electronic cam calculation part 22. FIG. On the other hand, when it is determined that the detection by the focus detection unit 21 is properly performed, an appropriate focus control that follows the movement of the subject is performed by using a signal indicating the in-focus state from the image sensor 6. Made.

  Next, the basic operation of zoom tracking will be described with reference to FIG. FIG. 3A is a diagram for explaining the concept of the zoom tracking operation, FIG. 3B is a diagram showing how zoom tracking is performed on a subject whose distance does not change, and FIG. 3C is a subject whose distance changes. It is a figure which shows a mode that zoom tracking is performed with respect to.

  In FIG. 3, the horizontal axis indicates the zoom position, the left side indicates the wide angle (WIDE) side, and the right side indicates the telephoto (TELE) side. The vertical axis represents the position of the focus lens, the lower side indicates the direction in which the focus lens approaches the image plane, and the upper side indicates the direction in which the focus lens approaches the subject. Also, the plurality of curves shown in FIGS. 3A, 3B, and 3C indicate the zoom position and focus for subjects with subject distances of 0.5 m, 1.0 m, 3.0 m, and infinity, respectively. The correspondence of lens positions is shown.

  As shown in FIG. 3, in order to focus on a subject at the same distance, it is necessary to move the position of the focus lens in accordance with the zoom position. Information about this curve is stored in the memory unit 8. In the electronic cam calculation unit 22, the amount by which the focus lens 31 is moved is calculated so as not to change the distance to the object-side surface at a position conjugate to the imaging element 6 in the imaging optical system 3 with respect to the zoom change. .

  In FIG. 3, reference numeral 30 denotes a zoom start point, reference numeral 40 denotes a zoom end point, and reference numeral 31 denotes a point indicating that a subject at a distance of 3.0 m at the zoom position 30 is in focus. Reference numeral 41 denotes a point indicating a state in which a subject at a distance of 3.0 m in the zoom state 40 is in focus.

  The basic operation of zoom tracking will be further described with reference to FIG. Consider a case where the zoom lens transitions from the zoom position 30 to the zoom position 40 when the subject is at a position 3.0 m from the imaging device. Although FIG. 3 does not express the concept of time, it is assumed here that the zoom position 30 has changed to the zoom position 40 in time series. When the subject at 3.0 m is in focus at the zoom position 30, the focus lens exists at the position indicated by 31. If the zoom position is changed to 40 while the focus lens is stopped, the state changes along the arrow 32 in FIG. Since the state 33 is located between the subject distance of 3.0 m and infinity, the subject farther than 3.0 m is in focus. In other words, the subject of 3.0m is out of focus. In order to focus on an object of 3.0 m at the zoom position 40, it is necessary to move the focus lens to a position indicated by 41.

  In the example of FIG. 3A, in order to make the explanation easy to understand, it has been described that the state is moved greatly in the zoom direction and the state 33 is changed to after the state 33 is reached. However, in practice, it is preferable to perform control so that the defocus amount generated in the state 33 and the state 41 is equal to or less than an allowable value. For this reason, it is desirable that the lens position sensor 15 has a resolution such that the state 33 and the state 41 in FIG.

  Compensating for the focus accompanying the zoom operation by some method is called zoom tracking in this embodiment. In zoom tracking, as a first tracking method, there is a method of performing zoom tracking by feeding back a signal using a focus detection sensor. As a second tracking method, there is a method of performing zoom tracking based on the positions of the focus lens and the zoom lens.

  In the present embodiment, a method of properly using the first tracking method and the second tracking method is used. The first tracking method feeds back a focus detection sensor signal (for example, a phase difference AF detection signal), and therefore has an advantage that no error is accumulated and a moving subject can easily follow. There is a problem that it does not work well when it is inappropriate. On the other hand, since the second tracking method is based on the signal from the position sensor, there is an advantage that the system configuration is easy. However, since the focus position of the final image is not used, errors such as the positioning of the sensor and the lens are not used. There are issues that tend to accumulate. In the present embodiment, in order to provide a high-quality image, the second tracking method is appropriately used to compensate for the disadvantage while taking advantage of the first tracking method.

  FIG. 3B is a diagram illustrating a state in which zoom tracking is appropriately performed on a subject whose distance does not change. In the first tracking method, the zoom operation is performed while the focus state is always kept in the in-focus state (transition from the zoom position 30 to the zoom position 40), so the state changes from 31 → 34 → 35 →. An appropriate zoom tracking operation is performed. On the other hand, in the second tracking method, the zoom sensor detects that the zoom state has changed and also detects the current position of the focus lens. In accordance with the change in the zoom position, the focus lens is positioned and controlled so as to focus on the subject at the same distance, that is, along a curve indicating that the subject at the same distance is in focus. Thus, an appropriate zoom tracking operation is performed.

  FIG. 3C is a diagram showing how zoom tracking is performed on a subject whose distance changes. Since the subject distance changes as will be described later, this corresponds to the case where zoom tracking and focusing are performed simultaneously instead of simple zoom tracking. In the first tracking method, as in the example of FIG. 3B, the zoom operation is always performed while the subject is in focus (transition from the zoom position 30 to the zoom position 40). The state changes from 31 → 36 → 37 →... → 42, and an appropriate zoom tracking operation is performed. On the other hand, the second tracking method tries to focus on a subject at the same distance, so if it is simply applied, it will not transition to state 42 as shown in FIG. However, control as shown in FIG. 3C is also possible by performing AF (autofocus) at an appropriate timing during zoom tracking to change the tracking curve. Thereby, an appropriate zoom tracking operation is performed.

  As described with reference to FIG. 3, in zoom tracking, when control is performed based on information related to the imaging state of the optical system (focus detection information or the like), simple control (always maintain an in-focus state) is possible. Appropriate operations can be performed on a moving subject. On the other hand, an error may occur because it is necessary to perform an advanced process of focus detection. In the present embodiment, this problem is solved.

  With reference to FIG. 4, the operation and effects of the present embodiment will be described. FIG. 4 is a graph using the same notation as FIG. 4 having the same meaning as in FIG. 3 are assigned the same numbers. FIG. 4 is a diagram showing a case where an error occurs during zoom tracking for a subject that has not moved. Although errors that are likely to occur will be described later, in phase difference AF (autofocus), the degree of coincidence of two images decreases, and a case where image coincidence between subjects that should not be dealt with is determined. .

  In FIG. 4, reference numeral 50 denotes a zoom position where the focus detection is inappropriate, 51 is an inappropriately acquired focus detection signal, and 51 a is a state used in place of 51. Assume that focus detection fails at the zoom position 50 in FIG. 4A and data 51 is obtained. That is, it is assumed that a focus detection result is obtained that the subject distance has moved to an infinite distance at the zoom position 50 even though the subject has not moved. If the position control of the focus lens is performed as it is, the state transitions from 31 → 34 → 51 →... → 41, and the focus state changes drastically on the way, resulting in a low quality image.

  When the focus detection result becomes unstable, as described above, such a result is obtained that the degree of coincidence between the two images is low, the change in the contrast signal is small, and the moving speed of the subject is too fast. Therefore, when the reliability determination unit 24 determines that the calculation result 51 at the zoom position 50 is inappropriate, the zoom tracking is performed based on the output of the electronic cam calculation unit 22. That is, referring to the immediately preceding state 34, the subject distance is obtained from the focus position and zoom position at this time. Assuming that the subject distance has not changed even at the zoom position 50, the position of the focus lens is obtained, and the state transitions to the state 51a. That is, as shown in FIG. 4B, the state transitions from 31 → 34 → 51a →. In this way, smooth focus control is performed. Appropriate lens control is performed even when an error occurs, and a high-quality image can be obtained stably.

  Next, another example will be described with reference to FIG. FIG. 5 is a graph using the same notation as FIG. 3 and FIG. 5 having the same meaning as those in FIGS. 3 and 4 are denoted by the same reference numerals.

  FIG. 5 (a) is a diagram showing the processing when the distance of the subject has changed after the error has occurred, and FIG. 5 (b) is during zoom tracking on the moving subject. It is the figure which showed the case where an error generate | occur | produced. FIG. 5 illustrates what control is performed using signals before and after an error occurs. Here, FIG. 5 is a graph that does not express the concept of time, but the zoom operation is performed at a constant speed, and the horizontal axis in the zoom direction corresponds to time.

  The example of FIG. 5A is a diagram illustrating a case where the subject has moved to 1.0 m at the next timing after an error has occurred in the zoom state 50. In FIG. 5A, in order to make the explanation easy to understand, the movement is made from 3.0 m to 1.0 m in one sampling, but this can be said to be very fast as a general subject moving speed. . In order to make the explanation when the distance of the subject has changed before and after the occurrence of the error easier to understand, this value is merely set for convenience.

  In FIG. 5A, it is assumed that the subject distance changes at the timing next to the occurrence of the error and the focus states 52 and 53 are obtained. In the operation of the present embodiment, as described with reference to FIG. 4, the focus lens position 51 a is set with reference to the state 34 immediately before the error, assuming that the subject distance does not change even at the zoom position 50. Determine. Next, when the subject distance is correctly obtained, the subject distance changes to 1.0 m. If the state is suddenly changed from 51a to 52 at this time, the focus change becomes too rapid, resulting in an image with low quality.

  Therefore, when the focus lens is controlled by the signal of the electronic cam calculation unit 22 when an error occurs, the control of the focus detection unit 21 is followed by the signal of the lens position sensor 15 in addition to the signal of the focus detection unit 21. Used to control the focus lens. Specifically, the difference 51a → 52 is filled in over several sampling times while referring to the lens position sensor 15. As another method, the movement amount per sampling may be limited. In the example of FIG. 5A, the state 52a is not shifted to the state 52, but a point 52a that is not too far from the current focus lens position obtained from the output of the lens position sensor 15 is set, and the state is shifted to this state. To do. Furthermore, when the state 53 is detected, the state 53a is transitioned to. In the example of FIG. 5A, the state transitions from 31 → 34 → 51a → 52a → 53a →.

  The example of FIG. 5B is a case where the subject is moving from 3.0 m to 1.0 m when an error occurs at the zoom position 50. It can be known from the state before the error occurs that the subject is moving. Therefore, when the focus lens is controlled by the signal from the electronic cam calculation unit 22, the focus lens is controlled by using a plurality of signals from the previous focus detection unit 21 in addition to the signal from the electronic cam calculation unit 22. To. Specifically, it can be seen that the subject is approaching when the state changes from 31 to 54. In order to determine the movement of the subject, a plurality of signals from the previous focus detection unit 21 may be used. Estimate the subject position at the zoom position 50 where the error occurred (for example, use a method such as predicting the position assuming that it is moving at a constant speed), and adjust the position of the focus lens so that the position is in focus. Control. In the example of FIG. 5B, the transition is made from 31 → 54 → 51b →.

  4 and 5 describe the case where an error occurs during the zoom operation, but there is no problem even if the operation of the present embodiment is performed when the zoom operation is not being performed. That is, the same effect is obtained in that the zoom tracking operation is not performed, and it is avoided that the focus state changes drastically in the middle due to an error, resulting in a low-quality image. In other words, there is no need to separate cases that are performed only during zoom operation.

  Next, the configuration of the image sensor 6 that supplies a signal to the focus detection unit 21 and the operation of the image processing unit 7 will be described with reference to FIG. The example of FIG. 6 shows a case where a so-called phase difference detection AF signal can be obtained by the image sensor 6.

  6A is a diagram for explaining the relationship between the image sensor 6 and the coordinate system, FIG. 6B is a diagram for explaining the division state of the pupil plane of the photographing optical system 3, and FIG. FIG. 6 is a diagram for explaining an image from one viewpoint obtained from the image sensor 6. FIG. 6D is a diagram for explaining an image from the other viewpoint obtained from the image sensor and a method of phase difference AF, and FIG. 6E is a diagram schematically showing a detection state of the phase difference AF. is there.

  6A, reference numeral 60 denotes a microlens array provided in the image sensor 6, 61 and 62 denote a plurality of pixels provided so as to correspond to one microlens, and 71 and 72 denote pixels 61 on the pupil plane. , 62 respectively. Also, 81 is an image acquired with pixels corresponding to the pupil region 71, 82 is a subject, 83 is a region of interest in the image 81, 84 is an image acquired with pixels corresponding to the pupil region 72, and 85 is a region of interest 83. And the same area in the screen. In addition, 86 is an arrow schematically indicating that searching is performed, 87 is an area in the image 84 corresponding to the area 83 of the image 81, 88 is an image obtained by superimposing images acquired from two viewpoints, and 89 is an image. The vectors detected in a region 83 in 81 are shown.

  As shown in FIG. 6A, a microlens array 60 is provided on the image sensor 6, and the front principal point of the microlens array 60 is arranged in the vicinity of the imaging plane of the photographing optical system 3. ing. FIG. 6A shows a state in which the microlens array 60 is viewed from the side and from the front of the imaging device. When viewed from the front of the imaging device, the lens of the microlens array 60 covers the pixels on the imaging device 6. Is arranged. In FIG. 6A, the microlens array 60 is illustrated in a large size so that the microlens array 60 can be easily seen. However, each microlens is actually large enough to cover two pixels.

  FIG. 6B is a diagram in which attention is paid to one microlens of the image sensor 6 and the underlying pixel, and the image sensor 6 is cut so that the longitudinal direction of the image sensor 6 includes the optical axis of the microlens and the horizontal direction of the figure. is there. Reference numerals 61 and 62 in FIG. 6B each denote a pixel (one photoelectric conversion unit) of the image sensor 6. On the other hand, the figure shown above FIG. 6B shows the exit pupil plane of the photographing optical system 3. Actually, when the direction is aligned with the image sensor shown in the lower part of FIG. 6B, the exit pupil plane is in the direction perpendicular to the plane of FIG. 6B, but the projection direction is used for easy understanding. Is changing.

  The pixels 61 and 62 in FIG. 6B are in a positional relationship corresponding to the regions 71 and 72 on the exit pupil plane that are in a conjugate positional relationship by the microlens 60, respectively. As shown in FIG. 6B, each pixel is designed to be conjugate with a specific region on the exit pupil plane of the photographing optical system 3 by the micro lens 60. That is, only the light beam that has passed through the region 71 on the exit pupil plane of the photographing optical system 3 enters the pixel 61, and only the light beam that has passed through the region 72 on the exit pupil surface of the photographing optical system 3 enters the pixel 61. .

  An image in which only pixels having the same correspondence as the pixel 61 that captures only the light beam that has passed through the pupil region 71 and a pixel that has the same corresponding relationship as the pixel 62 in which only the light beam that has passed through the pupil region 72 are captured are collected. Considering the image, it is an image with a different viewpoint. An image obtained by collecting only pixels having the same correspondence as the pixel 61 is an image as seen from the pupil region 71, and an image obtained by collecting only pixels having the same correspondence as the pixel 62 is viewed from the pupil region 72. It is an image. That is, if exposure is performed once and signals are arranged appropriately, images with different viewpoints exposed at the same timing can be obtained.

  Next, a method of performing focus detection (focus state detection) using two images acquired from different viewpoints will be described with reference to FIGS. Two images 81 and 84 acquired from different viewpoints are acquired by the optical system described with reference to FIGS. 6 (a) and 6 (b). Of these, attention is paid to an area 83 where the subject 82 exists in one image 81. The size of this area can be set arbitrarily, but it may be 8 × 8 pixels, for example. In the example of FIG. 6, the frame is shown sufficiently large for easy understanding.

  What is necessary is just to search where the area | region 83 moved to the image 84 on the basis of a difference absolute value (= SAD). Specifically, the SAD may be calculated while shifting the area as indicated by an arrow 86 in a predetermined range around the area 85 corresponding to the position in the image 84 in the image 84. In this case, the arrow 86 indicating the direction in which the region is shifted may be set in the direction connecting the centroids of the two pupil regions shown in FIG. This is because there is a so-called epipolar constraint. When SAD is used as a reference, the minimum position is the corresponding area 87. As a result, it can be seen that the region 83 has moved like a vector 89 in the composite image 88 of the two images. The direction of the vector 89 indicates the direction of the focus lens to be moved when focusing, and the length of the vector 89 indicates the amount of the focus lens that should be moved when focusing.

  When focus detection is performed according to the principle described with reference to FIGS. 6C, 6D, and 6E, when the specularly reflected light looks different depending on the viewpoint, and when there is an object similar to a distant and short distance, a repetitive pattern Errors are likely to occur when observing In such a case, the degree of coincidence of the two images decreases, or a phenomenon in which a plurality of similar peaks are seen and judgment cannot be made.

  In FIG. 6, focus detection is performed based on the principle of so-called phase difference AF. As another method, a method based on contrast AF is also conceivable. In this method, the focus lens is slightly driven in time series to observe the contrast change in the region of interest. This is a method of controlling the focus so that the contrast is maximized. In contrast AF, signals are generally extracted in time series, and therefore errors are likely to occur when there is a change in illumination state, a change in camera shake state, or when the subject moves.

  Next, an example in which an error occurs in focus detection will be described with reference to FIG. In FIG. 7, reference numeral 91 denotes an example of an image in which a subject having a portion similar to a distant place and a close distance exists, and 92 and 93 denote frames indicating similar regions, respectively. Reference numeral 94 denotes an example of an image where a subject with specular reflection light exists, 95 denotes a subject, and 96 denotes specular reflection light on the subject.

  FIG. 7A is a diagram for explaining an image in which a subject having a portion similar to a distant place and a close distance exists. Assume that the area for focus detection described in FIG. Near the boundary between the hat and the brim of the hat. If the subject behind also wears the same color hat, region 92 has a similar signal. If it is determined that the area 93 and the area 92 correspond to each other due to the influence of noise or the like, the focus detection results in an error. However, in such a case, it is possible to obtain information that it is difficult to distinguish from the case of correctly handling. That is, there is obtained information that there are two local minimum values of SAD, and both of them look the same. In the present embodiment, the reliability determination unit 24 determines that an error has occurred using this.

  FIG. 7B is a diagram illustrating an image in which a subject with specularly reflected light exists. When light from a strong light source such as sunlight hits the subject 95, the signal of the regular reflection light 96 appears strongly. In the case of a curved surface such as a sphere, this specularly reflected light component is observed at a different position on the subject 95 depending on the viewpoint. For this reason, when the phase difference AF is detected by the regular reflection light component, the focus detection becomes an error. However, in such a case, information is observed that the degree of coincidence between the two images decreases because the contour portion of the subject and the specularly reflected light are observed at different positions. In the present embodiment, the reliability determination unit 24 determines that an error has occurred using this.

  In a situation where an error is likely to occur in the actual operating environment as described above, a case where AF becomes unstable is assumed. In such a case, the position of the focus lens is controlled by performing the operation of the present embodiment. It can be performed stably.

  As described above, according to the present embodiment, in a system that performs focus adjustment using a signal on the imaging surface, it is possible to perform appropriate lens control even when a focus detection error occurs, and stably achieve high quality. It is possible to provide a simple image.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

3: photographing optical system, 5: camera system control circuit, 6: imaging device, 7: image processing unit, 8: memory unit, 12: lens system control circuit, 13: lens driving unit, 15: lens position sensor, 21: Focus detection unit, 22: electronic cam calculation unit, 23: changeover switch, 24: reliability determination unit

Claims (11)

Focus detection means for detecting the focus state of the imaging optical system;
Zoom position detecting means for detecting the zoom position of the photographing optical system;
Focus position detection means for detecting the position of the focus lens of the photographing optical system;
Adjusting means for adjusting the position of the focus lens of the photographing optical system;
Storage means for storing a locus of the focus lens for continuously focusing on a subject at the same distance in accordance with a change in the zoom position;
Determination means for determining reliability of the output of the focus detection means;
Based on the first operation for controlling the position of the focus lens according to the change in the zoom position based on the output of the focus detection means, and on the locus information of the focus lens stored in the storage means. A control unit that switches a second operation for controlling the position of the focus lens in accordance with a change in the zoom position in accordance with the determination of the determination unit;
An imaging apparatus comprising:   The control unit performs the first operation when the determination unit determines that the output of the focus detection unit is reliable, and the determination unit has no reliability in the output of the focus detection unit. The imaging apparatus according to claim 1, wherein the second operation is performed when the determination is made.   The control means controls the position of the focus lens using the output of the focus detection means in addition to the information on the locus of the focus lens stored in the storage means when performing the second operation. The imaging apparatus according to claim 2, wherein:   The control unit uses the plurality of outputs of the focus detection unit immediately before the determination unit determines that the output of the focus detection unit is unreliable in addition to information on the locus of the focus lens. The image pickup apparatus according to claim 3, wherein the position of the image pickup device is controlled.   The control means, when performing the first operation, controls the position of the focus lens by using the output of the focus position detection means in addition to the output of the focus detection means. Item 3. The imaging device according to Item 2.   When the focus state of the photographing optical system is detected by phase difference detection, the determination unit determines that the output of the focus detection unit is not reliable when the degree of coincidence of the two images for detecting the phase difference is low. The imaging apparatus according to claim 1, wherein:   When the determination unit detects the focus state of the photographing optical system by phase difference detection, and there are a plurality of peaks in the image for detecting the phase difference, the output of the focus detection unit is not reliable. The imaging device according to claim 1, wherein the imaging device is determined.   6. The determination unit according to claim 1, wherein the determination unit determines that the output of the focus detection unit is unreliable when there is a subject having specular reflection light in the image. Imaging device. A method for controlling an imaging device, comprising:
A focus detection step for detecting the focus state of the imaging optical system;
A zoom position detecting step for detecting a zoom position of the photographing optical system;
A focus position detecting step for detecting the position of the focus lens of the photographing optical system;
An adjustment step of adjusting the position of the focus lens of the photographing optical system;
A storage step of storing a locus of the focus lens for continuously focusing on a subject at the same distance according to a change in the zoom position;
A determination step of determining the reliability of the output of the focus detection step;
Based on the first operation for controlling the position of the focus lens in accordance with the change in the zoom position based on the output of the focus detection step, and on the locus information of the focus lens stored in the storage step. A control step of switching a second operation for controlling the position of the focus lens in accordance with a change in the zoom position according to the determination in the determination step;
A method for controlling an imaging apparatus, comprising:   The program for making a computer perform each process of the control method of Claim 9.   A computer-readable storage medium storing a program for causing a computer to execute each step of the control method according to claim 9.

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